GAZA, April 2 (Reuters) - Israeli planes and helicopters mounted at least seven missile attacks on the Hamas-ruled Gaza Strip on Friday, destroying what a military spokesman described as Palestinian munitions sites. Four air strikes blew up two caravans near the town of Khan Younis, witnesses and Hamas officials said. There were no casualties.

A fifth missile hit a cheese factory in Gaza City, setting it on fire, witnesses and Hamas officials said. Hospital officials said two children were slightly wounded by flying debris.

Helicopters struck twice in the central refugee camp of Nusseirat, destroying a metal foundry. There were no casualties.

An Israeli military spokesman confirmed the attacks, saying they had targeted two weapons-manufacturing plants and two arms caches.

The air strikes were Israel's response to a Palestinian short-range rocket that was fired across the border into the Jewish state on Thursday, the spokesman said. The attack, which went unclaimed by any Palestinian faction, caused no damage.

An Israeli offensive in the Gaza Strip early last year was designed to counter such salvoes. Rocket attacks have resumed sporadically in recent weeks and Israel has responded with air strikes.